le fou

My Feedback: (12)

Hi,

I am putting the two wing halves from my extra 300S from great planes (ARF) together but I do not obtain the same incidence when I join them together. There is a difference of about 1 degree. The trailing edge and leading edge are aligned. What do you suggest I do to fix the problem?

Thanks,

Le fou

freeair

what you need to do firstly is find which wing halve is out with the tailplane incidence, tailplane should be 0 degrees as so the main wing. to get the wing halve thats out of degrees correct you need to elonggate the front and rear guide pin holes in the fuselage side so you get the degrees you want. when your happy with this you then need to epoxy a sleeve into the oval shaped hole in fuse so both front and rear pin holes are back to the round shape so when you fit the wing halve all is spot on every time.

outdoorhunting

You didn't say if the wing-half was straight from root to the tip, or if the wing-half itself was twisted. If the wing-half itself is twisted, you might be able to "jig it up" & use heat on the covering to "straighten it. I'm thinking, if the wing is twisted & you don't staighten it first, the fix that freeair explained could make it worse. If it "is straight" then freeair is right on. !!!! I might be tottaly wrong, (somebody correct me if needed) 1degree might not be any big deal, it would be "trimmable" when you set up the ailerons. Good luck

le fou

My Feedback: (12)

I don't think that I was clear enough - I haven't glued the wing together yet.

opjose

You said that the trailing and leading edges are aligned.

Does that mean, to each other?

If so where are you measuring the difference in incidence?

le fou

My Feedback: (12)

Yes they are aligned to each other. I use a Robart incidence meter that I attach at the end of each wing.

nmking09

My Feedback: (61)

Is this the new extra 300sp that has a plug in wing or the old 300s that has a one piece wing?

pimmnz

It sounds like one of your panels is twisted. Set the tip up at some angle, then measure the root with the incidence meter. They should both be the same. If they are not then either replace the panel, or attempt to twist it back to alignment, if possible. The re-twist needs to be permanent. If none of these solutions is possible, then you have to make a judgment as to how much this twist will affect the lateral trim of the model, will the tip being out a little have more effect than the root being out a little? On a straight, constant chord wing it will, on a highly tapered wing, it won't. So when you glue the panels together, either set the root the same as the other wing, or set the tip, or somewhere between the two depending on the amount of taper of the panel. The end result is to try to have the average wing chord line set the same as the other panel, so that there is as little difference in average AOA between each wing panel as you can get. It will be a compromise, at the stall angle one tip will be at a slightly different angle than the other so the stall will not be symmetric, but it is probably the best compromise you can get.
Evan, WB #12.